This invention pertains to a cooling device for a hermetic motor-compressor unit, and more particularly to a cooling device that radially sprays a portion of the lubricant pumped by a lubricant pick-up tube directly against the lower end turns of the motor stator.
One problem of major concern relating to hermetic motor-compressor units is the heat generated by its operation which decreases compressor cooling efficiency. Various devices have been arranged within the housing of the motor-compressor unit to pump lubricant from an oil sump therein onto or against different structural members to reduce their temperatures caused by the heat generated by the unit's operation. An example of one such device is disclosed in U.S. Pat. No. 3,618,337 wherein a portion of the pumped lubricant is used to cool the lower end ring of the rotor and thereafter the lower end turns of the stator. In particular, oil flows from the oil sump up through an oil pick-up tube into a chamber, which is formed by the inner surfaces of the rotor end ring, a radially disposed flange of the pick-up tube, and the rotating crankshaft. Passages are radially provided in the rotor end ring so that the oil within the chamber may pass therethrough and be dispersed against the stator lower end turns for the cooling thereof. However, since the lubricant must first pass through passages in the rotor end rings before contacting the stator lower end turns, the cooling experienced by the stator lower end turns is reduced because of the increase in temperature of the lubricant as it passes through the radial passages removing heat energy from the rotor end ring.
A further disadvantage of the device disclosed in U.S. Pat. No. 3,618,337 is the increase in cost resulting from the structure defining the oil chamber, i.e., the rotor end ring, the radially disposed flange of the pick-up tube, and the fastener assemblies required to attach the radial flange to the rotor end ring lower surfaces, and the drilling of a plurality of radial passages in the rotor end ring.
Another prior art device similar to the above-mentioned prior art device is disclosed in U.S. Pat. No. 3,560,116 wherein oil is delivered by a pump into two streams, one stream being used for normal lubricating purposes associated with the parts disposed in the upper housing area, and a second stream for cooling the motor parts directly. The two streams of oil are created by two oil pump pick-up tubes, an inner tube and an outer tube, wherein the outer tube pumps lubricant upwardly through the area defined between the inner and outer tube into a chamber defined by the rotor lower short-circuiting ring, a flange radially disposed on the top portion of the outer tube, and the inner tube which extends upwardly to the rotating crankshaft. The radial flange has depressed grooves radially disposed therein and with the lower surface of the lower short-circuiting ring form radial passages for delivering a portion of the lubricant therethrough against the stator lower coil ends. Any cooling experienced by the stator lower coil ends is reduced since the oil being sprayed thereon has absorbed heat energy from the radial flange, inner pick-up tube, and the rotor lower short-circuiting ring. As with the prior art cooling device disclosed in the above U.S. Pat. No. 3,618,337, the temperature of the rotor is generally higher than the temperature of the stator, thereby further reducing any cooling effect of the oil against the stator lower coil ends.
Further, the cooling device in U.S. Pat. No. 3,560,116 undesirably increases the cost of the compressor because of its rather complex construction requiring two coaxially disposed pick-up tubes, the radial flange disposed on the upper portion of the outer pick-up tube, and the depressed grooves disposed within the radial flange.